The present invention relates to an image processing method, a recording medium, and an image processing apparatus, which smooth electronic data pertaining to an input image and eliminate noise.
In the case of an image input device such as a digital still camera (hereinafter simply called a “digital camera”) utilizing an image input element; e.g., a CCD, the image input element outputs an undesired electrical signal as well as an electrical signal corresponding to the amount of received light. As a result, the thus-output undesired electrical signal is included, as noise, in electronic data constituting an image. Noise tends to appear noticeably in a portion of the electrical signal having low luminance; that is, in a dark image portion.
In order to eliminate such noise in the image, there has hitherto been employed a method of smoothing all electronic data constituting an image or eliminating noise from an image in accordance with edge information.
However, when all electronic data constituting an image have been subjected to smoothing, all electronic data are subjected to smoothing despite differences in luminance from one area to another within an image. As a result, not only a portion of electronic data which has low luminance and involves conspicuous noise, but also a portion of the data which has high luminance and involves comparatively-less-conspicuous noise is smoothed, thereby deteriorating sharpness of an image. Consequently, noise concentrated at a low-luminance portion cannot be eliminated effectively.
Even in the case of a method of eliminating noise in accordance with edge information, there also arises a problem of enhancement of noise existing in a flat portion other than the edge regions.